The invention relates to an improved structure and technique for dissipating the heat generated by integrated circuit semiconductor chips.
With the advance of solid state electronics, various improved means of dissipating the heat generated by the solid state components have been investigated. The standard forced air convection means appears to have reached its limits of practicality in that the amount of air that is required to provide sufficient cooling for the limited heat dissipating surfaces introduces a noise problem, and without some auxiliary techniques cannot maintain each of a large number of components, such as integrated circuit semiconductor chips, within their proper operating temperature range. Accordingly, especially in connection with high speed data processing systems and the like, combinations of air-liquid cooling systems have been divised. One such system is an immersion cooling system, wherein the array of components to be cooled is immersed in a tank of cooling liquid. The liquids frequently employed are the fluorocarbon liquids which have a low-boiling point. These liquids are dielectric and give rise to various types of boiling at relatively low temperature. In view of the problems encountered in servicing and packaging components which are cooled using the immersion technique, an encapsulated cooling technique was provided which includes the same dielectric material encapsulated separately for each module.
U.S. Pat. No. 3,741,292 issued June 26, 1973 shows an example of a module having the heat generating components located thereon surrounded by a low boiling point dielectric liquid which is encapsulated thereto. A vapor space is located above the liquid level, which is filled with internal fins extending into the container serving as a condenser for the dielectric liquid vapors. External fins extend outward from the container and serve as an air cooled sink for the internal fins condenser. However, this type of a modular liquid encapsulated cooling device must meet certain inflexible requirements. For instance, it requires coolant of extremely high purity and free of any contaminants. Its operation is sensitive to all the variables which govern the basic process of nucleate boiling and vapor condensation. Furthermore, the concept is not readily adaptable to small scale applications such as a single heat generating component or semiconductor chip.
Reference is made to U.S. Pat. No. 3,993,123 entitled "Gas Encapsulated Cooling Module" granted Nov. 23, 1976 to Richard C. Chu et al. In the Chu et al patent a gas encapsulated cooling unit is provided for one or more heat generating devices (such as semiconductor chips) to be cooled. The components are mounted on a substrate. A cap is sealed to the substrate enclosing the heat generating devices to be cooled. An inert gas and good thermal conductive elements are contained within the sealed volume between the cap and the substrate. Each of the heat conductive elements are urged against respective ones of the heat generating devices forming a small gas gap (interface) to provide low thermal resistance. A heat sink associated with the cap receives the heat from the heat conductive elements through an annular gap which likewise contains inert gas.
Reference is made to U.S. Pat. No. 4,138,692 entitled "Gas Encapsulated Cooling Module" granted Feb. 6, 1979 to Robert G. Meeker et al. The Meeker et al patent discloses a gas encapsulated cooling module wherein at least one semiconductor chip to be cooled is supported on a substrate portion of the module. The Meeker et al patent discloses provision of a heat sink stud having a planar surface in thermal contact with a planar surface of the chip to be cooled, said stud being supported by a resilient thermally conductive bellow-like structure, whereby the planar surface of the stud is maintained in intimate thermal contact with the planar surface of the chip.
Reference is made to U.S. Pat. No. 4,156,458 entitled "Flexible Thermal Connector For Enhancing Conduction Cooling" granted May 29, 1979 to R. C. Chu et al. The R. C. Chu et al patent discloses a flexible thermal connector which consists of a heat conductive metallic foil bundle of sufficient thickness to contact sufficient surface area of the heat source to provide the required heat transfer and of sufficient thinness to be flexible enough to absorb the expansion and contraction due to temperature changes as well as the differences in distance between the heat source and sink and of sufficient length to contact at or near the other end thereof the heat sink.
Reference is made to the IBM Technical Disclosure Bulletin publication entitled "Conduction Cooling" by R. C. Chu, Vol. 21, No. 2, July 1978, pages 752-3. In the Chu publication a plurality of pin-pistons provide a number of contact points between the heat sink and the semiconductor chip.
Reference is made to the IBM Technical Disclosure Bulletin publication entitled "Serrated Pistons For Improved Module Cooling" by S. Oktay et al., Vol. 21, No. 5, October 1978, pages 1858-9. In the Oktay et al publication, the module uses pistons in removing heat by conduction from semiconductor chips. Truncated pyramidal shapes at the piston end improve contact to the chip. The piston has a cross-sectional geometry of a spline, modified spline, pinion gear or similar cross-section. The geometry provides a substantial increase in surface area at the annulus of the piston-to-module housing, thereby reducing the overall thermal resistance.
Reference is made to the IBM Technical Disclosure Bulletin publication entitled "Brush-Tipped Piston for Thermal Conduction" by R. G. Dessauer et al., Vol. 21, No. 5, October 1978, page 1857. The Dessauer et al publication discloses thermal conduction from a semiconductor chip on a substrate to a piston contained in a module cap. A number of wires extend from the piston and contact the planar surface of the semiconductor chip. The wires are deformed by spring loading the piston.